Home directories are given automatically to everyone who has a CS account. The amount of disk space depends on your default group. Should there be a legitimate need (and it doesn't fall into the project category), quotas can be increased upon request, subject to approval, using the form located in the "Request Forms" block on each page of the CS guide.
How do I determine my disk quota/usage?
You can find your quota space usage by logging into the CS Guide. If you are not logged in, there will be a "User login" block on this page. Once logged in, you will see blocks showing your home directory and email usage/quota. You can also view your email quota in real-time (which includes any other data stored under Webmail). See the EMail Quota page for details.